- Data structures https://developer.apple.com/documentation/foundation/collections?language=objc
- Archiving and serialization https://developer.apple.com/documentation/foundation/archives_and_serialization?language=objc
- Networking basics
- UIView and CALayer
- UIControls - button, textfield/view, label (string and attributed string), switch, image view, tab bar item, navigation bar, https://developer.apple.com/documentation/uikit/views_and_controls?language=objc
- Events https://developer.apple.com/documentation/uikit/touches_presses_and_gestures/using_responders_and_the_responder_chain_to_handle_events?language=objc
- Basics of Auto Layout
- Handling rotations
- Localization
- I18n (Left to Right)
- Animations (Key based animations)
- View Controller custom presentations and transitions https://developer.apple.com/library/archive/featuredarticles/ViewControllerPGforiPhoneOS/CustomizingtheTransitionAnimations.html
- View controller custom push transitions (and edge swipes)
- Safe Area
- A11y
- Collection views - custom layout
- Text Layout Programming Guide https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/TextLayout/TextLayout.html#//apple_ref/doc/uid/10000158-SW1
- UIApplicationDelegate methods